Underwater sound signal for explosive echo ranging

ABSTRACT

A bomb-type underwater sound signal source is disclosed wherein the explosive charge is in the form of an explosive cord which is normally coiled within the bomb casing and automatically deployed upon impact with the sea surface. The extended cord trails behind the bomb until it is detonated at a preset depth to produce an acoustic signal substantially confined to a horizontal plane.

United States Patent 1151 3,701,319 Axelson et al. [4 1 Oct. 31,1972

[54] UNDERWATER SOUND SIGNAL FOR 2,820,971 1/1958 Welsh et a1. ..102/13X EXPLOSIVE ECHO RANGING 3,351,010 11] 1967 Ainslie et al ..l02/4 [72]Inventors: Carl A. Axelson, 190 McKay Street, 3354826 H1967 f et "102/10Beverly, Mass. 019 5; J R. 3,408,935 11/1968 Biggs, Jr. ..102/4 Hinves,249 Caroline Avenue, Somerset, Mass. 02725; Elton Y. PrimaryExaminer--Samuel W. Engle McGann, 2l4 Kingswood Drive, Attorney-R. S.Sciacia and L. l. Shrago Williamsburg, Va. 23185; Robert M. Johnson, 110Green Briar Drive, 57 ABSTRACT Clarks Green, Pa. 1841 l A bomb-typeunderwater sound signal source is dis- [22] Flled: 1970 closed whereinthe explosive charge is in the form of [21] Appl. No.: 93,977 anexplosive cord which is normally coiled within the bomb casing andautomatically deployed upon impact [52] U S CL 102/7 102/10 102/22 withthe sea surface. The extended cord trails behind 51 111001..I:11111111111111: ..f ..F42 b 21/00 the it is dammed a P1"asetdepth [58] Field of Search ..102/2, 4, 7, 10, 13, 22 Produce an acousticSignal Substantially confined to a horizontal plane. [56] ReferencesClted 2 Claims, 3 Drawing Figures UNITED STATES PATENTS 3,276,366l0/l966 Johnson et a1 ..l02/7 Z1 za V4 lll// L UNDERWATER SOUND SIGNALFOR EXPLOSIVE ECHO RANGING The invention described herein may bemanufactured and used by or for the Government of the United States ofAmerica for governmental purposes without the payment of any royaltiesthereon or therefor.

The present invention relates to a line charge bomb which may bedetonated at various depths to generate an acoustic signal which isconcentrated in a horizontal plane.

In US. Pat. No. 3,276,366, which has as inventors, coinventors of thepresent application, there is disclosed a line charge bomb which isdetonated when a pressure disk included in the firing mechanism isruptured at a predetermined hydrostatic pressure. When this ruptureoccurs, a tail portion of the bomb assembly is disconnected and ejectedvertically by a coiled spring. Stored in the casing is a roll of sheetexplosive and, as the tail portion travels upwardly, this sheet isunrolled and assumes a vertical position so that when it is subsequentlyfired it acts as a line charge. The radiated acoustic energy isconsequently substantially confined to a horizontal plane. This type ofradiation pattern is desirable since, for example, it minimizes surfaceand bottom reverberations which might otherwise obscure target echosignals.

One of the critical features of the above bomb is that deployment of theline charge must take place within a short time after the pressure diskassembly ruptures. Although a connector link of an ignition substance isincluded to provide a time delay, there is the possibility of prematureignition of the sheet explosive when it is only partially uncoiled. Ifthis happens, the acoustic energy will be radiated omnidirectionallyinstead of in the preferred horizontal plane. It has also beendetermined that there is some tendency for the rolled sheet explosive tobecome jammed within the casing and not uncoil when a tension is appliedthereto by the upward movement of the tail assembly.

It is accordingly a primary object of the present invention to provide aline charge bomb wherein the line charge is deployed in a verticalposition shortly after the bomb impacts the sea surface.

Another object of the present invention is to provide a line charge bombwhich utilizes a rolled explosive cord which is automatically deployedin response to the water splash and thereafter trails behind the bomb asit falls within the fluid medium to the preselected depth at whichdetonation occurs.

A still further object of the present invention is to provide a bomb foraircraft launch wherein a length of explosive cord stored within thetail assembly is streamed by the water splash and thereafter explodedfrom the bottom upwardly to produce a sound pattern wherein most of theacoustic energy is radiated in a horizontal plane.

Other objects, advantages and novel features of the invention willbecome apparent from the following detailed description of the inventionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a partial section through the assembled line charge bombshowing the apparatus in its standby condition;

FIG. 2 is a sectional view taken along line A-A showing how theexplosive cord is stored in the bomb casing;

FIG. 3 shows the details of a gripping device which is connected to thefree end of the explosive cord and the strain cord; and

FIG. 4 shows the line charge bomb after the explosive cord has beendeployed.

Referring now to FIG. 1 of the drawings, it will be seen that the bombassembly consists of a nose section 1 containing the firing mechanism, amidsection 2 containing the main explosive charge, and a tail section 3.

Nose section 1 is similar in all important aspects to the same sectionin the above-identified patent and, as described therein, includes anarming piston that is initially locked in place by a safety rod which issecured to a drag plate that fits into the tail fins 30. As is wellknown, when the bomb assembly is dropped from an aircraft, theaerodynamic drag forces acting on the drag plate withdraw the safety rodfrom the piston so that after the bomb enters the ocean the hydrostaticpressures may act on the arming piston and move a spring-biased delaycharge into alignment with a firing pin and an aperture whichcommunicates with the midsection 2. The precise manner in which thedelay detonator is triggered is fully disclosed in the above patent and,consequently, no further description of this aspect of the presentinvention is deemed necessary. However, it would be pointed out thatwhen the present bomb finally reaches a predetermined depth, the delaydetonator is exploded and the explosive force is directed through thecommunicating aperture against one exposed end of an explosive cord 4which, as will be seen hereinafter, has previously been deployed fromthe tail section 3 of the bomb and is fully extended in a substantiallyvertical direction.

Tail section 3 accommodates in a rear portion thereof a deploymentmember 5 which has a cylindrical body portion that effectively closesthis end of the tail. This deployment member, which may be made ofplastic, has a rear flared skirt portion 6 which extends outwardlybeyond the narrow neck portion 7 of the tail section. This member islocked in place by an arcuated spring 9 that clips around acircumferential portion of the narrow neck section 7 and maintains adetent ball partially within an aperture cut through the wall portion ofthe tail section and a circular groove 10 formed in the body portion ofthe deployment member adjacent one end thereof. When clip spring 9 is inplace, it will be appreciated, detent ball 8 latches deployment member 5in the position shown and prevents its longitudinal movement out theopen end of the tail section 3.

Stored within the midsection 2 of the bomb assembly is the line chargeexplosive which consists of a suitable length of explosive cord 4. Thiscord is in fact a plastic explosive covered by a nylon jacket. As bestshown in FIG. 2, the cord is stored in a figure eight within anoval-shaped cavity 12 formed in the casing 13 of this section. Bywrapping the explosive cord in this configuration, any possible kinksare eliminated and the subsequent payout of the cord is accomplishedwith little likelihood of entanglement.

One end of cord 4, which extends into the tail section 3, has a cablegripping means 14 affixed thereto. This gripping means, as best shown inFIG. 3, comprises an arcuated metallic strap 15 that is formed with aplurality of depending projections, such as l6, l7, and 18, that arepressed through the nylon jacket and into the plastic explosive. Asuitable pressure-sensitive tape 19 is wrapped about this strap so as tokeep it from spreading apart after it has once been bent in place. Alength of nylon line 20 connects strap 15 to the deployment member 5.More particularly, a central passageway is cut throughout the length ofmember 5, and one end of the nylon 20 is led therethrough and knotted at21. The other end of the nylon line passes through a suitable aperturecut in the nose portion of strap 15 and is also knotted at 22.

The other end of explosive cord 4 fits within an aperture formed in acentral hub portion 23 of the midsection casing 2. This aperture isenlarged with respect to the thickness of the explosive cord so thatthis end of the cord may be securely fastened to the midsection 2 by apotting compound 24 in a manner which leaves its end face exposed.Closing this end of the midsection 2 is a circular plate 25 whichsupports a pickup cup 26 containing an explosive charge, maintaining itin intimate contact with this exposed face of the explosive cord and inalignment with the communicating aperture 27 in the nose section 1through which the explosive force of the delay detonator acts.

Midsection 2 also contains two pieces of sponge rubber 28 and 29 whichrest against the inner face of the central hub 23 and an inner rimportion of casing 13. These rubber pieces provide a spring force to keepthe explosive cord 4 in its assembled condition and, additionally, theyposition the cable gripping means 14 in the front portion of the tailsection so that the cord may be freely pulled out through this sectionat the appropriate time.

The operation of the line charge bomb is as follows: When the assembledapparatus, as shown in FIG. I, is launched from an aircraft, the airflow removes the drag plate from the tail fins and the safety wire isremoved from the arming piston. The bomb is now armed and firing of themain explosive can occur when the proper water depth is reached. As thebomb continues its air flight, deployment member remains held in placewithin the tail section 3 by the detent ball 8 and the cooperating,arcuated spring clip 9. However, when it enters the water, the force ofthe water splash, because of the narrow neck design of the tail section,is directed against the flared skirt 6 of the deployment member andurges this member out the tail section. The sloping surface of groovecams detent ball outwardly and forces spring clip 9 free. Deploymentmember 6 consequently is now unrestrained and the continuing forcesacting on it pushes it completely out of the tail section 3. As the bombassembly continues to fall within the ocean, the drag experienced bymember 5 gradually increases the separation between it and the bombassembly, resulting in a tension stress being applied to nylon line anda tightening of this line. Thereafter, continued descent of the bombcauses the explosive cord 4 to be gradually pulled through the tailsection until all of it has been uncoiled. Finally, the cord is fullydeployed and it continues, as shown in FIG. 4, to trail behind the bombuntil it reaches a depth where the firing mechanism actuates the delaydetonator and the resultant explosion triggers the pickup cup and thenthe inboard end of the explosive cord.

It will be appreciated that while the apparatus of FIG. 1 is shown witha detonating assembly of the t pe utilizing an arming piston, othertypes 0 detona ors may be used to detonate the explosive cup or theexplosive cord at the preset depth. Likewise, different types ofexplosive trains may be used to detonate the explosive cord and, thus,the pickup cup may not be needed in the overall apparatus.

What is claimed is:

1. In a bomb-type underwater acoustic signal source having a casing thatcontains in its nose section a detonating mechanism that detonates asecondary explosive charge also accommodated therein at a preselecteddepth and having a hollow, narrow neck, open-ended tail section whichcommunicates with the interior of said casing, the combination of alength of explosive cord coiled within the interior of said casing withone end thereof maintained in contact with said secondary explosivecharge;

a deployment member tied to the other end of said explosive cord,

said deployment member having a cylindrical body portion which slidablyfits within said openended tail section and closes off this section whenin place;

means for latching said deployment member in place; said deploymentmember also having a rear skirt which extends radially outward beyondsaid narrow neck such that when said deployment member is in place andsaid signal source enters the ocean nose first, hydrodynamic forces actupwardly on said skirt, said hydrodynamic forces, when sufficient,releasing said latching means and moving said deployment member out fromsaid tail section, the drag forces subsequently acting on saiddeployment member uncoiling and extracting said length of explosive cordout from said hollow tail section and causing said explosive cord to bemaintained in a vertical attitude as said casing falls to saidpreselected depth at which said explosive cord is exploded.

2. In an arrangement as defined in claim 1 wherein said deploymentmember has a circumferential groove formed in the cylindrical bodyportion thereof and said latching means includes an aperture formedthrough the wall of said tail section at a location adjacent that ofsaid circumferential groove when said deployment member is in place;

a detent ball; and

an arcuate spring clip positioned on said tail section over saidaperture and locking said detent ball partially within said aperture andsaid circumferential groove, 7

the hydrodynamic forces acting on the skirt of said deployment member,when sufficient, camming said detent ball outwardly and removing saidspring clip.

1. In a bomb-type underwater acoustic signal source having a casing thatcontains in its nose section a detonating mechanism that detonates asecondary explosive charge also accommodated therein at a preselecteddepth and having a hollow, narrow neck, open-ended tail section whichcommunicates with the interior of said casing, the combination of alength of explosive cord coiled within the interIor of said casing withone end thereof maintained in contact with said secondary explosivecharge; a deployment member tied to the other end of said explosivecord, said deployment member having a cylindrical body portion whichslidably fits within said open-ended tail section and closes off thissection when in place; means for latching said deployment member inplace; said deployment member also having a rear skirt which extendsradially outward beyond said narrow neck such that when said deploymentmember is in place and said signal source enters the ocean nose first,hydrodynamic forces act upwardly on said skirt, said hydrodynamicforces, when sufficient, releasing said latching means and moving saiddeployment member out from said tail section, the drag forcessubsequently acting on said deployment member uncoiling and extractingsaid length of explosive cord out from said hollow tail section andcausing said explosive cord to be maintained in a vertical attitude assaid casing falls to said preselected depth at which said explosive cordis exploded.
 2. In an arrangement as defined in claim 1 wherein saiddeployment member has a circumferential groove formed in the cylindricalbody portion thereof and said latching means includes an aperture formedthrough the wall of said tail section at a location adjacent that ofsaid circumferential groove when said deployment member is in place; adetent ball; and an arcuate spring clip positioned on said tail sectionover said aperture and locking said detent ball partially within saidaperture and said circumferential groove, the hydrodynamic forces actingon the skirt of said deployment member, when sufficient, camming saiddetent ball outwardly and removing said spring clip.